1. Technical Field
The present invention relates to a corrugator or corrugating machine and a method of operating the machine for making corrugated paperboard. More particularly, the present invention relates to a corrugator having a separation sensor which is used to sense separation of layers of the paperboard which have been glued together.
2. Background Information
Corrugators for making corrugated paperboard are well known, and are sometimes referred to as corrugating machines or corrugating lines which include a series of linked machines. Corrugated paperboard or corrugated board has a number of common uses, including the formation of corrugated boxes, mainly used for shipping and storage. Corrugated paperboard is typically made from rolls of liner or paperboard which are typically large rolls of wound paper which may stretch out over several miles when unwound. Corrugated paperboard is formed of wavy or fluted paper known as a corrugating or corrugated medium which is glued to a flat sheet typically called a liner. Corrugated board can thus be made up of one or more layers of the corrugated medium and one or more of the liners. For instance, a single liner glued to corrugated medium creates a singleface corrugated board. Corrugated medium glued between two flat liners forms a single wall corrugated board. The addition of another corrugated medium and third flat liner to the single wall corrugated board creates a double wall corrugated board. Triple wall corrugated boards may also be formed with three layers of corrugated medium and four flat liners glued to one another in a similar alternating configuration.
Corrugators operate such that the paperboard, liners or webs unwind rapidly off of wound rolls and move downstream typically at a rate of 500 lineal feet per minute or more. This rate is often up to or in excess of 1,000 feet per minute. During the formation process, one of the liners typically passes between two corrugating rolls which form the liner into the corrugated medium, which is subsequently glued to the other liner in order to form the singleface web noted above, which is a continuous sheet of flat paper with fluted paper or the corrugating medium glued to it. Before the liners reach the corrugating rolls and before being glued together, they are typically heated by heating rolls and exposed to steam applicators or showers. Glue is then typically applied to tips of the flutes of the corrugated medium in order to glue the corrugated medium to the flat liner to form the corrugated paperboard.
One of the problems that arises in the formation of the corrugated paperboard is the separation of the corrugated medium from the liner after it has been glued together. Such a separation can cause substantial problems at certain locations downstream of the gluing or joining of the liner and corrugated medium. Thus, it would be highly beneficial in order to ascertain the separation between the layers of paperboard relatively shortly downstream of the gluing station in order to prevent these problems further downstream. The present invention achieves this goal.